Rodríguez et al., 1999. Livest. Res. Rural Dev., 11 (1)

Eight chickens at point of lay, four of one of the indigenous ecotypes typically used in Vietnam and four of an exotic strain imported orginally from China (the Tam Hoang), scavenged during the day in an integrated  farm (planted with cassava, bananas and forage trees with recycling of wastes from pigs and chickens through biodigesters and ponds for duckweed and fish). In the late afternoon until the following morning the chickens were confined individually in bamboo cages with free access to rice bran, fresh duckweed and a 50:50 mixture (fresh weight basis) of the two offered in separate feeders. After a period of 8 weeks of adaptation to the cages and to the scavenging system, records were kept daily of feeds offered and refused during a period of 13 days. The birds were weighed at the beginning and end of the 13 day period and egg production was recorded.

There were major differences (P=0.001) between ecotypes in intake of duckweed offered as a single feed but not (P=0.18) when it was mixed with rice bran. As a consequence, total intake of duckweed (that offered separately plus that in the mixture) was almost twice as high (P=0.001) for the local chickens (65 g/day)  compared with the "exotic" Tam Hoang (38 g/day). Calculated levels of crude protein in the total diet dry matter were similar for both ecotypes  (15.9 and 15.2%) but the proportion of the protein derived from duckweed was almost 50% higher (20 versus 14%) for the local birds compared with the Tam Hoang.